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    <article class="post">
        <header>
            <h1 class="post-title">《在Flutter中的Sliver》</h1>
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        <date class="post-meta meta-date">
            2021年5月26日
        </date>
        
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            <span>|</span>
            
            <span class="meta-category"><a href='/categories/flutter'>flutter</a></span>
            
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            <span id="busuanzi_container_page_pv">|<span id="busuanzi_value_page_pv"></span><span>
                    阅读</span></span>
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                <div class="toc-title">文章目录</div>
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            <blockquote>
<p>本文主要介绍</p>
</blockquote>
<pre><code>CustomScrollView( ///视窗
        slivers: &lt;Widget&gt;[
          //转接器
SliverToBoxAdapter(child: FlutterLogo(
  size: 500,
),),SliverToBoxAdapter(child: FlutterLogo(
  size: 500,
),)


        
        ],
      )
</code></pre><pre><code> CustomScrollView(
        ///视窗
        slivers: &lt;Widget&gt;[
          //转接器

          SliverToBoxAdapter(
            child: Text(&quot;表头&quot;),
          ),
          SliverToBoxAdapter(
            child: Text(&quot;表头2&quot;),
          ),
          SliverToBoxAdapter(
            child: FlutterLogo(),
          ),
          SliverList(delegate: SliverChildBuilderDelegate((con, index) {
            return Container(
              height: 200,
              color: Colors.accents[index % 200],
            );
          }))
        ],
      )
</code></pre><pre><code>CustomScrollView(
        ///视窗
        slivers: &lt;Widget&gt;[
          //转接器

          SliverToBoxAdapter(
            child: Text(&quot;表头&quot;),
          ),
          SliverToBoxAdapter(
            child: Text(&quot;表头2&quot;),
          ),
          SliverGrid(
              delegate: SliverChildBuilderDelegate((con, index) {
                return Container(
                  height: 200,
                  color: Colors.accents[index % 18],
                );
              },childCount: 23),
              gridDelegate:
                  SliverGridDelegateWithFixedCrossAxisCount(crossAxisCount: 4)),
          SliverList(delegate: SliverChildBuilderDelegate((con, index) {
            return Container(
              height: 200,
              color: Colors.primaries[index % Colors.primaries.length],
            );
          }))
        ],
      )
</code></pre><p>用按钮的边框实现读秒功能https://dartpad.dev/517c90856bcb43c00e9367a71b75fd58</p>
<div class="highlight"><pre style="color:#f8f8f2;background-color:#272822;-moz-tab-size:4;-o-tab-size:4;tab-size:4"><code class="language-dart" data-lang="dart"><span style="color:#66d9ef">import</span> <span style="color:#e6db74">&#39;dart:math&#39;</span>;
<span style="color:#66d9ef">import</span> <span style="color:#e6db74">&#39;dart:ui&#39;</span> <span style="color:#66d9ef">as</span> ui;

<span style="color:#66d9ef">import</span> <span style="color:#e6db74">&#39;package:flutter/material.dart&#39;</span>;
<span style="color:#66d9ef">import</span> <span style="color:#e6db74">&#39;package:flutter/rendering.dart&#39;</span>;

<span style="color:#66d9ef">void</span> main() {
  runApp(MyApp());
}

<span style="color:#66d9ef">class</span> <span style="color:#a6e22e">MyApp</span> <span style="color:#66d9ef">extends</span> StatelessWidget {
  <span style="color:#960050;background-color:#1e0010">@</span>override
  Widget build(BuildContext context) {
    <span style="color:#66d9ef">return</span> MaterialApp(
      title: <span style="color:#e6db74">&#39;Flutter Demo&#39;</span>,
      theme: ThemeData(
        primarySwatch: Colors.blue,
        visualDensity: VisualDensity.adaptivePlatformDensity,
      ),
      home: MyHomePage(
        title: <span style="color:#e6db74">&#39;Lint&#39;</span>,
      ),
    );
  }
}

<span style="color:#66d9ef">class</span> <span style="color:#a6e22e">MyHomePage</span> <span style="color:#66d9ef">extends</span> StatefulWidget {
  MyHomePage({Key key, <span style="color:#66d9ef">this</span>.title}) <span style="color:#f92672">:</span> <span style="color:#66d9ef">super</span>(key: key);

  <span style="color:#66d9ef">final</span> <span style="color:#66d9ef">String</span> title;

  <span style="color:#960050;background-color:#1e0010">@</span>override
  _MyHomePageState createState() <span style="color:#f92672">=&gt;</span> _MyHomePageState();
}

<span style="color:#66d9ef">class</span> <span style="color:#a6e22e">_MyHomePageState</span> <span style="color:#66d9ef">extends</span> State<span style="color:#f92672">&lt;</span>MyHomePage<span style="color:#f92672">&gt;</span> {
  <span style="color:#960050;background-color:#1e0010">@</span>override
  <span style="color:#66d9ef">void</span> initState() {
    <span style="color:#66d9ef">super</span>.initState();
  }

  <span style="color:#960050;background-color:#1e0010">@</span>override
  Widget build(BuildContext context) {
    <span style="color:#66d9ef">return</span> Scaffold(
      appBar: AppBar(
        title: Text(widget.title),
      ),
      body: Center(
        child: Column(
          mainAxisAlignment: MainAxisAlignment.center,
          children: <span style="color:#f92672">&lt;</span>Widget<span style="color:#f92672">&gt;</span>[
            Countdown(
              radius: <span style="color:#ae81ff">35.0</span>,
              width: <span style="color:#ae81ff">180.0</span>,
              height: <span style="color:#ae81ff">70.0</span>,
              duration: Duration(seconds: <span style="color:#ae81ff">60</span>),
            ),
            SizedBox(height: <span style="color:#ae81ff">40</span>),
            Countdown(
              radius: <span style="color:#ae81ff">20.0</span>,
              width: <span style="color:#ae81ff">180.0</span>,
              height: <span style="color:#ae81ff">70.0</span>,
              duration: Duration(seconds: <span style="color:#ae81ff">10</span>),
            ),
            SizedBox(height: <span style="color:#ae81ff">40</span>),
            Countdown(
              radius: <span style="color:#ae81ff">0.0</span>,
              width: <span style="color:#ae81ff">180.0</span>,
              height: <span style="color:#ae81ff">70.0</span>,
              duration: Duration(seconds: <span style="color:#ae81ff">60</span>),
            ),
          ],
        ),
      ),
      floatingActionButton: FloatingActionButton(
        onPressed: () {},
        tooltip: <span style="color:#e6db74">&#39;Increment&#39;</span>,
        child: Icon(Icons.add),
      ),
    );
  }
}

enum Status { ready, animating, end }

<span style="color:#75715e">/// 这里还有2中情况还没考虑进去，后续有需要在写，目前能满足视频需求
</span><span style="color:#75715e"></span><span style="color:#66d9ef">class</span> <span style="color:#a6e22e">Countdown</span> <span style="color:#66d9ef">extends</span> StatefulWidget {
  <span style="color:#66d9ef">const</span> Countdown({<span style="color:#66d9ef">this</span>.radius <span style="color:#f92672">=</span> <span style="color:#ae81ff">0.0</span>, <span style="color:#960050;background-color:#1e0010">@</span>required <span style="color:#66d9ef">this</span>.width, <span style="color:#960050;background-color:#1e0010">@</span>required <span style="color:#66d9ef">this</span>.height, <span style="color:#960050;background-color:#1e0010">@</span>required <span style="color:#66d9ef">this</span>.duration});

  <span style="color:#66d9ef">final</span> <span style="color:#66d9ef">double</span> radius;
  <span style="color:#66d9ef">final</span> <span style="color:#66d9ef">double</span> width;
  <span style="color:#66d9ef">final</span> <span style="color:#66d9ef">double</span> height;
  <span style="color:#66d9ef">final</span> Duration duration;

  <span style="color:#960050;background-color:#1e0010">@</span>override
  _CountdownState createState() <span style="color:#f92672">=&gt;</span> _CountdownState();
}

<span style="color:#66d9ef">class</span> <span style="color:#a6e22e">_CountdownState</span> <span style="color:#66d9ef">extends</span> State<span style="color:#f92672">&lt;</span>Countdown<span style="color:#f92672">&gt;</span> <span style="color:#66d9ef">with</span> SingleTickerProviderStateMixin {
  AnimationController animationController;

  <span style="color:#75715e">/// 矩形顶部横线线 ，从中间开始到结束
</span><span style="color:#75715e"></span>  Animation<span style="color:#f92672">&lt;</span><span style="color:#66d9ef">double</span><span style="color:#f92672">&gt;</span> topEndLineAnimation;

  <span style="color:#75715e">/// 矩形右上角圆角
</span><span style="color:#75715e"></span>  Animation<span style="color:#f92672">&lt;</span><span style="color:#66d9ef">double</span><span style="color:#f92672">&gt;</span> topRightArcAnimation;

  <span style="color:#75715e">/// 矩形右边竖线
</span><span style="color:#75715e"></span>  Animation<span style="color:#f92672">&lt;</span><span style="color:#66d9ef">double</span><span style="color:#f92672">&gt;</span> rightLineAnimation;

  <span style="color:#75715e">/// 矩形右下角圆角
</span><span style="color:#75715e"></span>  Animation<span style="color:#f92672">&lt;</span><span style="color:#66d9ef">double</span><span style="color:#f92672">&gt;</span> bottomRightArcAnimation;

  <span style="color:#75715e">/// 矩形底部横线
</span><span style="color:#75715e"></span>  Animation<span style="color:#f92672">&lt;</span><span style="color:#66d9ef">double</span><span style="color:#f92672">&gt;</span> bottomLineAnimation;

  <span style="color:#75715e">/// 矩形左下角圆角
</span><span style="color:#75715e"></span>  Animation<span style="color:#f92672">&lt;</span><span style="color:#66d9ef">double</span><span style="color:#f92672">&gt;</span> bottomLeftArcAnimation;

  <span style="color:#75715e">/// 矩形左边竖线
</span><span style="color:#75715e"></span>  Animation<span style="color:#f92672">&lt;</span><span style="color:#66d9ef">double</span><span style="color:#f92672">&gt;</span> leftLineAnimation;

  <span style="color:#75715e">/// 矩形左上角圆角
</span><span style="color:#75715e"></span>  Animation<span style="color:#f92672">&lt;</span><span style="color:#66d9ef">double</span><span style="color:#f92672">&gt;</span> topLeftArcAnimation;

  <span style="color:#75715e">/// 矩形顶部横线线 ，从0开始到中间
</span><span style="color:#75715e"></span>  Animation<span style="color:#f92672">&lt;</span><span style="color:#66d9ef">double</span><span style="color:#f92672">&gt;</span> startTopLineAnimation;

  <span style="color:#75715e">/// 圆形
</span><span style="color:#75715e"></span>  Animation<span style="color:#f92672">&lt;</span><span style="color:#66d9ef">double</span><span style="color:#f92672">&gt;</span> circleAnimation;

  <span style="color:#75715e">/// 当前按钮状态
</span><span style="color:#75715e"></span>  Status _status <span style="color:#f92672">=</span> Status.ready;

  <span style="color:#75715e">/// 按钮半径
</span><span style="color:#75715e"></span>  <span style="color:#66d9ef">double</span> radius <span style="color:#f92672">=</span> <span style="color:#ae81ff">0.0</span>;

  <span style="color:#75715e">/// 按钮宽
</span><span style="color:#75715e"></span>  <span style="color:#66d9ef">double</span> width <span style="color:#f92672">=</span> <span style="color:#ae81ff">0.0</span>;

  <span style="color:#75715e">/// 按钮高
</span><span style="color:#75715e"></span>  <span style="color:#66d9ef">double</span> height <span style="color:#f92672">=</span> <span style="color:#ae81ff">0.0</span>;

  <span style="color:#75715e">/// 绘制动画时间
</span><span style="color:#75715e"></span>  Duration duration <span style="color:#f92672">=</span> <span style="color:#66d9ef">const</span> Duration(seconds: <span style="color:#ae81ff">0</span>);

  <span style="color:#75715e">/// 是否是矩形
</span><span style="color:#75715e"></span>  <span style="color:#66d9ef">bool</span> isRectangle() {
    <span style="color:#66d9ef">return</span> widget.radius <span style="color:#f92672">&lt;=</span> <span style="color:#ae81ff">0</span>;
  }

  <span style="color:#75715e">/// 是否是圆形
</span><span style="color:#75715e"></span>  <span style="color:#66d9ef">bool</span> isCircle() {
    <span style="color:#66d9ef">return</span> widget.height <span style="color:#f92672">==</span> widget.width <span style="color:#f92672">&amp;&amp;</span> widget.radius <span style="color:#f92672">&gt;=</span> widget.height <span style="color:#f92672">/</span> <span style="color:#ae81ff">2</span>;
  }

  <span style="color:#75715e">/// 是否是圆角矩形
</span><span style="color:#75715e"></span>  <span style="color:#66d9ef">bool</span> isArcRectangle() {
    <span style="color:#66d9ef">return</span> widget.radius <span style="color:#f92672">&gt;</span> <span style="color:#ae81ff">0</span> <span style="color:#f92672">&amp;&amp;</span> widget.height <span style="color:#f92672">/</span> <span style="color:#ae81ff">2</span> <span style="color:#f92672">&gt;</span> widget.radius <span style="color:#f92672">&amp;&amp;</span> widget.width <span style="color:#f92672">/</span> <span style="color:#ae81ff">2</span> <span style="color:#f92672">&gt;</span> widget.radius;
  }

  <span style="color:#75715e">/// 是否上下整个圆角
</span><span style="color:#75715e"></span>  <span style="color:#66d9ef">bool</span> isHeightArc() {
    <span style="color:#66d9ef">return</span> widget.radius <span style="color:#f92672">&gt;=</span> widget.width <span style="color:#f92672">/</span> <span style="color:#ae81ff">2</span> <span style="color:#f92672">&amp;&amp;</span> widget.height <span style="color:#f92672">&gt;</span> widget.width;
  }

  <span style="color:#75715e">/// 是否左右整个圆角
</span><span style="color:#75715e"></span>  <span style="color:#66d9ef">bool</span> isWidthArc() {
    <span style="color:#66d9ef">return</span> widget.radius <span style="color:#f92672">&gt;=</span> widget.height <span style="color:#f92672">/</span> <span style="color:#ae81ff">2</span> <span style="color:#f92672">&amp;&amp;</span> widget.width <span style="color:#f92672">&gt;</span> widget.height;
  }

  <span style="color:#75715e">/// 是否上下左右都是圆角
</span><span style="color:#75715e"></span>  <span style="color:#66d9ef">bool</span> isBothArc() {
    <span style="color:#66d9ef">return</span> widget.radius <span style="color:#f92672">&gt;=</span> widget.width <span style="color:#f92672">/</span> <span style="color:#ae81ff">2</span> <span style="color:#f92672">&amp;&amp;</span>
        widget.radius <span style="color:#f92672">&gt;=</span> widget.height <span style="color:#f92672">/</span> <span style="color:#ae81ff">2</span> <span style="color:#f92672">&amp;&amp;</span>
        (widget.radius <span style="color:#f92672">&lt;</span> widget.width <span style="color:#f92672">||</span> widget.radius <span style="color:#f92672">&lt;</span> widget.height);
  }

  <span style="color:#66d9ef">double</span> circleLength() {
    <span style="color:#66d9ef">return</span> <span style="color:#ae81ff">2</span> <span style="color:#f92672">*</span> pi <span style="color:#f92672">*</span> _radius();
  }

  <span style="color:#66d9ef">double</span> arcLength() {
    <span style="color:#66d9ef">return</span> circleLength() <span style="color:#f92672">/</span> <span style="color:#ae81ff">4</span>;
  }

  <span style="color:#66d9ef">double</span> squareLength() {
    <span style="color:#66d9ef">return</span> <span style="color:#ae81ff">2</span> <span style="color:#f92672">*</span> (widget.height <span style="color:#f92672">+</span> widget.width);
  }

  <span style="color:#66d9ef">double</span> arcSquareLength() {
    <span style="color:#66d9ef">final</span> <span style="color:#66d9ef">double</span> longLength <span style="color:#f92672">=</span> (widget.height <span style="color:#f92672">-</span> <span style="color:#ae81ff">2</span> <span style="color:#f92672">*</span> widget.radius) <span style="color:#f92672">*</span> <span style="color:#ae81ff">2</span>;
    <span style="color:#66d9ef">final</span> <span style="color:#66d9ef">double</span> widthLength <span style="color:#f92672">=</span> (widget.width <span style="color:#f92672">-</span> <span style="color:#ae81ff">2</span> <span style="color:#f92672">*</span> widget.radius) <span style="color:#f92672">*</span> <span style="color:#ae81ff">2</span>;
    <span style="color:#66d9ef">return</span> longLength <span style="color:#f92672">+</span> widthLength <span style="color:#f92672">+</span> circleLength();
  }

  <span style="color:#75715e">/// yuan
</span><span style="color:#75715e"></span>  <span style="color:#66d9ef">double</span> arcWidthSquareLength() {
    <span style="color:#66d9ef">final</span> <span style="color:#66d9ef">double</span> longLength <span style="color:#f92672">=</span> (widget.width <span style="color:#f92672">-</span> <span style="color:#ae81ff">2</span> <span style="color:#f92672">*</span> widget.radius) <span style="color:#f92672">*</span> <span style="color:#ae81ff">2</span>;
    <span style="color:#66d9ef">return</span> longLength <span style="color:#f92672">+</span> circleLength();
  }

  <span style="color:#66d9ef">double</span> _radius() {
    <span style="color:#66d9ef">if</span> (isCircle()) {
      <span style="color:#66d9ef">if</span> (widget.radius <span style="color:#f92672">&gt;</span> widget.height <span style="color:#f92672">/</span> <span style="color:#ae81ff">2</span> <span style="color:#f92672">||</span> widget.radius <span style="color:#f92672">&gt;</span> widget.width <span style="color:#f92672">/</span> <span style="color:#ae81ff">2</span>) {
        <span style="color:#66d9ef">return</span> widget.height <span style="color:#f92672">/</span> <span style="color:#ae81ff">2</span>;
      }
    }
    <span style="color:#66d9ef">if</span> (isWidthArc()) {
      <span style="color:#66d9ef">return</span> widget.height <span style="color:#f92672">/</span> <span style="color:#ae81ff">2</span>;
    }
    <span style="color:#66d9ef">return</span> widget.radius <span style="color:#f92672">??</span> <span style="color:#ae81ff">0</span>;
  }

  <span style="color:#960050;background-color:#1e0010">@</span>override
  <span style="color:#66d9ef">void</span> initState() {
    <span style="color:#66d9ef">super</span>.initState();
    width <span style="color:#f92672">=</span> widget.width;
    height <span style="color:#f92672">=</span> widget.height;
    radius <span style="color:#f92672">=</span> widget.radius;
    duration <span style="color:#f92672">=</span> widget.duration;
    animationController <span style="color:#f92672">=</span> AnimationController(vsync: <span style="color:#66d9ef">this</span>)..duration <span style="color:#f92672">=</span> widget.duration <span style="color:#f92672">??</span> <span style="color:#66d9ef">const</span> Duration(seconds: <span style="color:#ae81ff">5</span>);
    _initAnimate();
  }

  <span style="color:#960050;background-color:#1e0010">@</span>override
  <span style="color:#66d9ef">void</span> didUpdateWidget(covariant Countdown oldWidget) {
    width <span style="color:#f92672">=</span> widget.width;
    height <span style="color:#f92672">=</span> widget.height;
    radius <span style="color:#f92672">=</span> widget.radius;
    duration <span style="color:#f92672">=</span> widget.duration;
    <span style="color:#66d9ef">super</span>.didUpdateWidget(oldWidget);
    <span style="color:#66d9ef">if</span> (oldWidget <span style="color:#f92672">!=</span> widget) {
      _initAnimate();
    }
  }

  <span style="color:#66d9ef">void</span> _initAnimate() {
    animationController.addListener(() {
      setState(() {
        <span style="color:#66d9ef">if</span> (animationController.isCompleted) {
          _status <span style="color:#f92672">=</span> Status.end;
        }
      });
    });

    <span style="color:#66d9ef">if</span> (isCircle()) {
      circleAnimation <span style="color:#f92672">=</span> Tween<span style="color:#f92672">&lt;</span><span style="color:#66d9ef">double</span><span style="color:#f92672">&gt;</span>(begin: <span style="color:#ae81ff">0.0</span>, end: <span style="color:#ae81ff">1.0</span>).animate(animationController);
    } <span style="color:#66d9ef">else</span> <span style="color:#66d9ef">if</span> (isRectangle()) {
      <span style="color:#66d9ef">final</span> <span style="color:#66d9ef">double</span> totalLength <span style="color:#f92672">=</span> squareLength();
      <span style="color:#66d9ef">final</span> <span style="color:#66d9ef">double</span> widthTime <span style="color:#f92672">=</span> width <span style="color:#f92672">/</span> totalLength <span style="color:#f92672">/</span> <span style="color:#ae81ff">2</span>;
      <span style="color:#66d9ef">final</span> <span style="color:#66d9ef">double</span> heightTime <span style="color:#f92672">=</span> height <span style="color:#f92672">/</span> totalLength;
      topEndLineAnimation <span style="color:#f92672">=</span> Tween<span style="color:#f92672">&lt;</span><span style="color:#66d9ef">double</span><span style="color:#f92672">&gt;</span>(begin: <span style="color:#ae81ff">0.0</span>, end: <span style="color:#ae81ff">1.0</span>)
          .animate(CurvedAnimation(parent: animationController, curve: Interval(<span style="color:#ae81ff">0</span>, widthTime)));
      rightLineAnimation <span style="color:#f92672">=</span> Tween<span style="color:#f92672">&lt;</span><span style="color:#66d9ef">double</span><span style="color:#f92672">&gt;</span>(begin: <span style="color:#ae81ff">0.0</span>, end: <span style="color:#ae81ff">1.0</span>)
          .animate(CurvedAnimation(parent: animationController, curve: Interval(widthTime, widthTime <span style="color:#f92672">+</span> heightTime)));
      bottomLineAnimation <span style="color:#f92672">=</span> Tween<span style="color:#f92672">&lt;</span><span style="color:#66d9ef">double</span><span style="color:#f92672">&gt;</span>(begin: <span style="color:#ae81ff">0.0</span>, end: <span style="color:#ae81ff">1.0</span>).animate(CurvedAnimation(
          parent: animationController, curve: Interval(widthTime <span style="color:#f92672">+</span> heightTime, widthTime <span style="color:#f92672">*</span> <span style="color:#ae81ff">3</span> <span style="color:#f92672">+</span> heightTime)));
      leftLineAnimation <span style="color:#f92672">=</span> Tween<span style="color:#f92672">&lt;</span><span style="color:#66d9ef">double</span><span style="color:#f92672">&gt;</span>(begin: <span style="color:#ae81ff">0.0</span>, end: <span style="color:#ae81ff">1.0</span>).animate(CurvedAnimation(
          parent: animationController, curve: Interval(widthTime <span style="color:#f92672">*</span> <span style="color:#ae81ff">3</span> <span style="color:#f92672">+</span> heightTime, widthTime <span style="color:#f92672">*</span> <span style="color:#ae81ff">3</span> <span style="color:#f92672">+</span> heightTime <span style="color:#f92672">*</span> <span style="color:#ae81ff">2</span>)));
      startTopLineAnimation <span style="color:#f92672">=</span> Tween<span style="color:#f92672">&lt;</span><span style="color:#66d9ef">double</span><span style="color:#f92672">&gt;</span>(begin: <span style="color:#ae81ff">0.0</span>, end: <span style="color:#ae81ff">1.0</span>)
          .animate(CurvedAnimation(parent: animationController, curve: Interval(widthTime <span style="color:#f92672">*</span> <span style="color:#ae81ff">3</span> <span style="color:#f92672">+</span> heightTime <span style="color:#f92672">*</span> <span style="color:#ae81ff">2</span>, <span style="color:#ae81ff">1</span>)));
    } <span style="color:#66d9ef">else</span> <span style="color:#66d9ef">if</span> (isWidthArc()) {
      <span style="color:#66d9ef">final</span> <span style="color:#66d9ef">double</span> totalLength <span style="color:#f92672">=</span> arcWidthSquareLength();
      <span style="color:#66d9ef">final</span> <span style="color:#66d9ef">double</span> startLineTime <span style="color:#f92672">=</span> (widget.width <span style="color:#f92672">-</span> <span style="color:#ae81ff">2</span> <span style="color:#f92672">*</span> widget.radius) <span style="color:#f92672">/</span> <span style="color:#ae81ff">2</span> <span style="color:#f92672">/</span> totalLength;
      <span style="color:#66d9ef">final</span> <span style="color:#66d9ef">double</span> arcTime <span style="color:#f92672">=</span> circleLength() <span style="color:#f92672">/</span> <span style="color:#ae81ff">2</span> <span style="color:#f92672">/</span> totalLength;
      topEndLineAnimation <span style="color:#f92672">=</span> Tween<span style="color:#f92672">&lt;</span><span style="color:#66d9ef">double</span><span style="color:#f92672">&gt;</span>(begin: <span style="color:#ae81ff">0.0</span>, end: <span style="color:#ae81ff">1.0</span>)
          .animate(CurvedAnimation(parent: animationController, curve: Interval(<span style="color:#ae81ff">0.0</span>, startLineTime)));
      topRightArcAnimation <span style="color:#f92672">=</span> Tween<span style="color:#f92672">&lt;</span><span style="color:#66d9ef">double</span><span style="color:#f92672">&gt;</span>(begin: <span style="color:#ae81ff">0.0</span>, end: <span style="color:#ae81ff">1.0</span>).animate(
          CurvedAnimation(parent: animationController, curve: Interval(startLineTime, startLineTime <span style="color:#f92672">+</span> arcTime)));
      bottomLineAnimation <span style="color:#f92672">=</span> Tween<span style="color:#f92672">&lt;</span><span style="color:#66d9ef">double</span><span style="color:#f92672">&gt;</span>(begin: <span style="color:#ae81ff">0.0</span>, end: <span style="color:#ae81ff">1.0</span>).animate(CurvedAnimation(
          parent: animationController, curve: Interval(startLineTime <span style="color:#f92672">+</span> arcTime, startLineTime <span style="color:#f92672">*</span> <span style="color:#ae81ff">3</span> <span style="color:#f92672">+</span> arcTime)));
      topLeftArcAnimation <span style="color:#f92672">=</span> Tween<span style="color:#f92672">&lt;</span><span style="color:#66d9ef">double</span><span style="color:#f92672">&gt;</span>(begin: <span style="color:#ae81ff">0.0</span>, end: <span style="color:#ae81ff">1.0</span>).animate(CurvedAnimation(
          parent: animationController, curve: Interval(startLineTime <span style="color:#f92672">*</span> <span style="color:#ae81ff">3</span> <span style="color:#f92672">+</span> arcTime, startLineTime <span style="color:#f92672">*</span> <span style="color:#ae81ff">3</span> <span style="color:#f92672">+</span> arcTime <span style="color:#f92672">*</span> <span style="color:#ae81ff">2</span>)));
      startTopLineAnimation <span style="color:#f92672">=</span> Tween<span style="color:#f92672">&lt;</span><span style="color:#66d9ef">double</span><span style="color:#f92672">&gt;</span>(begin: <span style="color:#ae81ff">0.0</span>, end: <span style="color:#ae81ff">1.0</span>)
          .animate(CurvedAnimation(parent: animationController, curve: Interval(startLineTime <span style="color:#f92672">*</span> <span style="color:#ae81ff">3</span> <span style="color:#f92672">+</span> arcTime <span style="color:#f92672">*</span> <span style="color:#ae81ff">2</span>, <span style="color:#ae81ff">1.0</span>)));
    } <span style="color:#66d9ef">else</span> {
      <span style="color:#66d9ef">final</span> <span style="color:#66d9ef">double</span> totalLength <span style="color:#f92672">=</span> arcSquareLength();
      <span style="color:#66d9ef">final</span> <span style="color:#66d9ef">double</span> leftLineTime <span style="color:#f92672">=</span> (widget.height <span style="color:#f92672">-</span> <span style="color:#ae81ff">2</span> <span style="color:#f92672">*</span> widget.radius) <span style="color:#f92672">/</span> totalLength;
      <span style="color:#66d9ef">final</span> <span style="color:#66d9ef">double</span> topLineTime <span style="color:#f92672">=</span> (widget.width <span style="color:#f92672">-</span> <span style="color:#ae81ff">2</span> <span style="color:#f92672">*</span> widget.radius) <span style="color:#f92672">/</span> <span style="color:#ae81ff">2</span> <span style="color:#f92672">/</span> totalLength;
      <span style="color:#66d9ef">final</span> <span style="color:#66d9ef">double</span> arcTime <span style="color:#f92672">=</span> arcLength() <span style="color:#f92672">/</span> totalLength;
      topEndLineAnimation <span style="color:#f92672">=</span> Tween<span style="color:#f92672">&lt;</span><span style="color:#66d9ef">double</span><span style="color:#f92672">&gt;</span>(begin: <span style="color:#ae81ff">0.0</span>, end: <span style="color:#ae81ff">1.0</span>)
          .animate(CurvedAnimation(parent: animationController, curve: Interval(<span style="color:#ae81ff">0.0</span>, topLineTime)));
      topRightArcAnimation <span style="color:#f92672">=</span> Tween<span style="color:#f92672">&lt;</span><span style="color:#66d9ef">double</span><span style="color:#f92672">&gt;</span>(begin: <span style="color:#ae81ff">0.0</span>, end: <span style="color:#ae81ff">1.0</span>)
          .animate(CurvedAnimation(parent: animationController, curve: Interval(topLineTime, topLineTime <span style="color:#f92672">+</span> arcTime)));
      rightLineAnimation <span style="color:#f92672">=</span> Tween<span style="color:#f92672">&lt;</span><span style="color:#66d9ef">double</span><span style="color:#f92672">&gt;</span>(begin: <span style="color:#ae81ff">0.0</span>, end: <span style="color:#ae81ff">1.0</span>).animate(CurvedAnimation(
          parent: animationController, curve: Interval(topLineTime <span style="color:#f92672">+</span> arcTime, topLineTime <span style="color:#f92672">+</span> arcTime <span style="color:#f92672">+</span> leftLineTime)));
      bottomRightArcAnimation <span style="color:#f92672">=</span> Tween<span style="color:#f92672">&lt;</span><span style="color:#66d9ef">double</span><span style="color:#f92672">&gt;</span>(begin: <span style="color:#ae81ff">0.0</span>, end: <span style="color:#ae81ff">1.0</span>).animate(CurvedAnimation(
          parent: animationController,
          curve: Interval(topLineTime <span style="color:#f92672">+</span> arcTime <span style="color:#f92672">+</span> leftLineTime, topLineTime <span style="color:#f92672">+</span> arcTime <span style="color:#f92672">*</span> <span style="color:#ae81ff">2</span> <span style="color:#f92672">+</span> leftLineTime)));
      bottomLineAnimation <span style="color:#f92672">=</span> Tween<span style="color:#f92672">&lt;</span><span style="color:#66d9ef">double</span><span style="color:#f92672">&gt;</span>(begin: <span style="color:#ae81ff">0.0</span>, end: <span style="color:#ae81ff">1.0</span>).animate(CurvedAnimation(
          parent: animationController,
          curve: Interval(topLineTime <span style="color:#f92672">+</span> arcTime <span style="color:#f92672">*</span> <span style="color:#ae81ff">2</span> <span style="color:#f92672">+</span> leftLineTime, topLineTime <span style="color:#f92672">*</span> <span style="color:#ae81ff">3</span> <span style="color:#f92672">+</span> arcTime <span style="color:#f92672">*</span> <span style="color:#ae81ff">2</span> <span style="color:#f92672">+</span> leftLineTime)));
      bottomLeftArcAnimation <span style="color:#f92672">=</span> Tween<span style="color:#f92672">&lt;</span><span style="color:#66d9ef">double</span><span style="color:#f92672">&gt;</span>(begin: <span style="color:#ae81ff">0.0</span>, end: <span style="color:#ae81ff">1.0</span>).animate(CurvedAnimation(
          parent: animationController,
          curve: Interval(topLineTime <span style="color:#f92672">*</span> <span style="color:#ae81ff">3</span> <span style="color:#f92672">+</span> arcTime <span style="color:#f92672">*</span> <span style="color:#ae81ff">2</span> <span style="color:#f92672">+</span> leftLineTime, topLineTime <span style="color:#f92672">*</span> <span style="color:#ae81ff">3</span> <span style="color:#f92672">+</span> arcTime <span style="color:#f92672">*</span> <span style="color:#ae81ff">3</span> <span style="color:#f92672">+</span> leftLineTime)));
      leftLineAnimation <span style="color:#f92672">=</span> Tween<span style="color:#f92672">&lt;</span><span style="color:#66d9ef">double</span><span style="color:#f92672">&gt;</span>(begin: <span style="color:#ae81ff">0.0</span>, end: <span style="color:#ae81ff">1.0</span>).animate(CurvedAnimation(
          parent: animationController,
          curve: Interval(
              topLineTime <span style="color:#f92672">*</span> <span style="color:#ae81ff">3</span> <span style="color:#f92672">+</span> arcTime <span style="color:#f92672">*</span> <span style="color:#ae81ff">3</span> <span style="color:#f92672">+</span> leftLineTime, topLineTime <span style="color:#f92672">*</span> <span style="color:#ae81ff">3</span> <span style="color:#f92672">+</span> arcTime <span style="color:#f92672">*</span> <span style="color:#ae81ff">3</span> <span style="color:#f92672">+</span> leftLineTime <span style="color:#f92672">*</span> <span style="color:#ae81ff">2</span>)));
      topLeftArcAnimation <span style="color:#f92672">=</span> Tween<span style="color:#f92672">&lt;</span><span style="color:#66d9ef">double</span><span style="color:#f92672">&gt;</span>(begin: <span style="color:#ae81ff">0.0</span>, end: <span style="color:#ae81ff">1.0</span>).animate(CurvedAnimation(
          parent: animationController,
          curve: Interval(
              topLineTime <span style="color:#f92672">*</span> <span style="color:#ae81ff">3</span> <span style="color:#f92672">+</span> arcTime <span style="color:#f92672">*</span> <span style="color:#ae81ff">3</span> <span style="color:#f92672">+</span> leftLineTime <span style="color:#f92672">*</span> <span style="color:#ae81ff">2</span>, topLineTime <span style="color:#f92672">*</span> <span style="color:#ae81ff">3</span> <span style="color:#f92672">+</span> arcTime <span style="color:#f92672">*</span> <span style="color:#ae81ff">4</span> <span style="color:#f92672">+</span> leftLineTime <span style="color:#f92672">*</span> <span style="color:#ae81ff">2</span>)));
      startTopLineAnimation <span style="color:#f92672">=</span> Tween<span style="color:#f92672">&lt;</span><span style="color:#66d9ef">double</span><span style="color:#f92672">&gt;</span>(begin: <span style="color:#ae81ff">0.0</span>, end: <span style="color:#ae81ff">1.0</span>).animate(CurvedAnimation(
          parent: animationController, curve: Interval(topLineTime <span style="color:#f92672">*</span> <span style="color:#ae81ff">3</span> <span style="color:#f92672">+</span> arcTime <span style="color:#f92672">*</span> <span style="color:#ae81ff">4</span> <span style="color:#f92672">+</span> leftLineTime <span style="color:#f92672">*</span> <span style="color:#ae81ff">2</span>, <span style="color:#ae81ff">1.0</span>)));
    }
  }

  <span style="color:#66d9ef">void</span> _changeStatus() {
    <span style="color:#66d9ef">switch</span> (_status) {
      <span style="color:#66d9ef">case</span> Status.ready:
        setState(() {
          _status <span style="color:#f92672">=</span> Status.animating;
          animationController.forward();
        });

        <span style="color:#66d9ef">break</span>;
      <span style="color:#66d9ef">case</span> Status.animating:
        setState(() {
          _status <span style="color:#f92672">=</span> Status.ready;
          animationController.reset();
        });
        <span style="color:#66d9ef">break</span>;
      <span style="color:#66d9ef">case</span> Status.end:
        <span style="color:#66d9ef">break</span>;
    }
  }

  <span style="color:#960050;background-color:#1e0010">@</span>override
  Widget build(BuildContext context) {
    <span style="color:#66d9ef">return</span> Container(
      child: GestureDetector(
        onTap: _changeStatus,
        child: Container(
          width: widget.width,
          height: widget.height,
          child: CustomPaint(
            painter: CountdownPainter(
              isRectangle: isRectangle(),
              isBothArc: isBothArc(),
              isWidthArc: isWidthArc(),
              isHeightArc: isHeightArc(),
              isCircle: isCircle(),
              isArcRectangle: isArcRectangle(),
              status: _status,
              endTopLine: topEndLineAnimation<span style="color:#f92672">?</span>.value <span style="color:#f92672">??</span> <span style="color:#ae81ff">0</span>,
              topRightArc: topRightArcAnimation<span style="color:#f92672">?</span>.value <span style="color:#f92672">??</span> <span style="color:#ae81ff">0</span>,
              rightLine: rightLineAnimation<span style="color:#f92672">?</span>.value <span style="color:#f92672">??</span> <span style="color:#ae81ff">0</span>,
              bottomRightArc: bottomRightArcAnimation<span style="color:#f92672">?</span>.value <span style="color:#f92672">??</span> <span style="color:#ae81ff">0</span>,
              bottomLine: bottomLineAnimation<span style="color:#f92672">?</span>.value <span style="color:#f92672">??</span> <span style="color:#ae81ff">0</span>,
              bottomLeftArc: bottomLeftArcAnimation<span style="color:#f92672">?</span>.value <span style="color:#f92672">??</span> <span style="color:#ae81ff">0</span>,
              leftLine: leftLineAnimation<span style="color:#f92672">?</span>.value <span style="color:#f92672">??</span> <span style="color:#ae81ff">0</span>,
              topLeftArc: topLeftArcAnimation<span style="color:#f92672">?</span>.value <span style="color:#f92672">??</span> <span style="color:#ae81ff">0</span>,
              startTopLine: startTopLineAnimation<span style="color:#f92672">?</span>.value <span style="color:#f92672">??</span> <span style="color:#ae81ff">0</span>,
              radius: _radius(),
              circle: circleAnimation<span style="color:#f92672">?</span>.value <span style="color:#f92672">??</span> <span style="color:#ae81ff">0</span>,
            ),
          ),
        ),
      ),
    );
  }
}

<span style="color:#75715e">/// 自定义绘画控件
</span><span style="color:#75715e"></span><span style="color:#66d9ef">class</span> <span style="color:#a6e22e">CountdownPainter</span> <span style="color:#66d9ef">extends</span> CustomPainter {
  CountdownPainter({
    <span style="color:#66d9ef">this</span>.isHeightArc <span style="color:#f92672">=</span> <span style="color:#66d9ef">false</span>,
    <span style="color:#66d9ef">this</span>.isWidthArc <span style="color:#f92672">=</span> <span style="color:#66d9ef">false</span>,
    <span style="color:#66d9ef">this</span>.isRectangle <span style="color:#f92672">=</span> <span style="color:#66d9ef">true</span>,
    <span style="color:#66d9ef">this</span>.isCircle <span style="color:#f92672">=</span> <span style="color:#66d9ef">false</span>,
    <span style="color:#66d9ef">this</span>.isBothArc <span style="color:#f92672">=</span> <span style="color:#66d9ef">false</span>,
    <span style="color:#66d9ef">this</span>.isArcRectangle <span style="color:#f92672">=</span> <span style="color:#66d9ef">false</span>,
    <span style="color:#66d9ef">this</span>.status <span style="color:#f92672">=</span> Status.ready,
    <span style="color:#66d9ef">this</span>.endTopLine <span style="color:#f92672">=</span> <span style="color:#ae81ff">0.0</span>,
    <span style="color:#66d9ef">this</span>.topRightArc <span style="color:#f92672">=</span> <span style="color:#ae81ff">0.0</span>,
    <span style="color:#66d9ef">this</span>.rightLine <span style="color:#f92672">=</span> <span style="color:#ae81ff">0.0</span>,
    <span style="color:#66d9ef">this</span>.bottomRightArc <span style="color:#f92672">=</span> <span style="color:#ae81ff">0.0</span>,
    <span style="color:#66d9ef">this</span>.bottomLine <span style="color:#f92672">=</span> <span style="color:#ae81ff">0.0</span>,
    <span style="color:#66d9ef">this</span>.bottomLeftArc <span style="color:#f92672">=</span> <span style="color:#ae81ff">0.0</span>,
    <span style="color:#66d9ef">this</span>.leftLine <span style="color:#f92672">=</span> <span style="color:#ae81ff">0.0</span>,
    <span style="color:#66d9ef">this</span>.topLeftArc <span style="color:#f92672">=</span> <span style="color:#ae81ff">0.0</span>,
    <span style="color:#66d9ef">this</span>.startTopLine <span style="color:#f92672">=</span> <span style="color:#ae81ff">0.0</span>,
    <span style="color:#66d9ef">this</span>.circle <span style="color:#f92672">=</span> <span style="color:#ae81ff">0.0</span>,
    <span style="color:#66d9ef">this</span>.radius <span style="color:#f92672">=</span> <span style="color:#ae81ff">0.0</span>,
  });

  <span style="color:#75715e">/// 是否圆形
</span><span style="color:#75715e"></span>  <span style="color:#66d9ef">final</span> <span style="color:#66d9ef">bool</span> isCircle;

  <span style="color:#75715e">/// 是否矩形
</span><span style="color:#75715e"></span>  <span style="color:#66d9ef">final</span> <span style="color:#66d9ef">bool</span> isRectangle;
  <span style="color:#66d9ef">final</span> <span style="color:#66d9ef">bool</span> isHeightArc;
  <span style="color:#66d9ef">final</span> <span style="color:#66d9ef">bool</span> isWidthArc;
  <span style="color:#66d9ef">final</span> <span style="color:#66d9ef">bool</span> isBothArc;

  <span style="color:#75715e">/// 是否圆角矩形
</span><span style="color:#75715e"></span>  <span style="color:#66d9ef">final</span> <span style="color:#66d9ef">bool</span> isArcRectangle;
  <span style="color:#66d9ef">final</span> <span style="color:#66d9ef">double</span> radius;
  <span style="color:#66d9ef">final</span> <span style="color:#66d9ef">double</span> endTopLine;
  <span style="color:#66d9ef">final</span> <span style="color:#66d9ef">double</span> topRightArc;
  <span style="color:#66d9ef">final</span> <span style="color:#66d9ef">double</span> rightLine;
  <span style="color:#66d9ef">final</span> <span style="color:#66d9ef">double</span> bottomRightArc;
  <span style="color:#66d9ef">final</span> <span style="color:#66d9ef">double</span> bottomLine;
  <span style="color:#66d9ef">final</span> <span style="color:#66d9ef">double</span> bottomLeftArc;
  <span style="color:#66d9ef">final</span> <span style="color:#66d9ef">double</span> leftLine;
  <span style="color:#66d9ef">final</span> <span style="color:#66d9ef">double</span> topLeftArc;
  <span style="color:#66d9ef">final</span> <span style="color:#66d9ef">double</span> startTopLine;
  <span style="color:#66d9ef">final</span> <span style="color:#66d9ef">double</span> circle;

  <span style="color:#66d9ef">final</span> Status status;

  <span style="color:#66d9ef">final</span> Paint paintArc <span style="color:#f92672">=</span> Paint()
    ..style <span style="color:#f92672">=</span> PaintingStyle.stroke
    ..color <span style="color:#f92672">=</span> Colors.grey
    ..strokeWidth <span style="color:#f92672">=</span> <span style="color:#ae81ff">3</span>;

  <span style="color:#66d9ef">final</span> Paint rectPaint <span style="color:#f92672">=</span> Paint()..strokeWidth <span style="color:#f92672">=</span> <span style="color:#ae81ff">3</span>;

  Color _rectColor() {
    <span style="color:#66d9ef">return</span> status <span style="color:#f92672">==</span> Status.end <span style="color:#f92672">?</span> Colors.grey <span style="color:#f92672">:</span> Colors.blue;
  }

  PaintingStyle _rectPaintingStyle() {
    <span style="color:#66d9ef">return</span> status <span style="color:#f92672">==</span> Status.ready <span style="color:#f92672">?</span> PaintingStyle.fill <span style="color:#f92672">:</span> PaintingStyle.stroke;
  }

  <span style="color:#75715e">/// 绘制矩形
</span><span style="color:#75715e"></span>  <span style="color:#66d9ef">void</span> _drawRect(Canvas canvas, Size size) {
    rectPaint
      ..color <span style="color:#f92672">=</span> _rectColor()
      ..style <span style="color:#f92672">=</span> _rectPaintingStyle();
    <span style="color:#66d9ef">final</span> RRect outRect <span style="color:#f92672">=</span> RRect.fromLTRBR(<span style="color:#ae81ff">0</span>, <span style="color:#ae81ff">0</span>, size.width, size.height, Radius.circular(radius));
    canvas.drawRRect(outRect, rectPaint);
  }

  Color _textColor() {
    <span style="color:#66d9ef">switch</span> (status) {
      <span style="color:#66d9ef">case</span> Status.animating:
        <span style="color:#66d9ef">return</span> Colors.blue;
      <span style="color:#66d9ef">case</span> Status.end:
        <span style="color:#66d9ef">return</span> Colors.grey;
      <span style="color:#66d9ef">case</span> Status.ready:
      <span style="color:#66d9ef">default</span><span style="color:#f92672">:</span>
        <span style="color:#66d9ef">return</span> Colors.white;
    }
  }

  <span style="color:#66d9ef">String</span> _text() {
    <span style="color:#66d9ef">switch</span> (status) {
      <span style="color:#66d9ef">case</span> Status.animating:
        <span style="color:#66d9ef">return</span> <span style="color:#e6db74">&#39;取消&#39;</span>;
      <span style="color:#66d9ef">case</span> Status.end:
        <span style="color:#66d9ef">return</span> <span style="color:#e6db74">&#39;完成&#39;</span>;
      <span style="color:#66d9ef">case</span> Status.ready:
      <span style="color:#66d9ef">default</span><span style="color:#f92672">:</span>
        <span style="color:#66d9ef">return</span> <span style="color:#e6db74">&#39;开始&#39;</span>;
    }
  }

  <span style="color:#75715e">/// 绘制文字
</span><span style="color:#75715e"></span>  <span style="color:#66d9ef">void</span> _drawText(Canvas canvas, Size size) {
    <span style="color:#66d9ef">final</span> <span style="color:#66d9ef">double</span> width <span style="color:#f92672">=</span> size.width;
    <span style="color:#66d9ef">final</span> <span style="color:#66d9ef">double</span> height <span style="color:#f92672">=</span> size.height;
    <span style="color:#66d9ef">final</span> ui.ParagraphBuilder builder <span style="color:#f92672">=</span> ui.ParagraphBuilder(ui.ParagraphStyle(
      textAlign: TextAlign.center,
      fontWeight: FontWeight.w600,
      fontStyle: FontStyle.normal,
      fontSize: <span style="color:#ae81ff">18</span>,
    ))
      ..pushStyle(ui.TextStyle(color: _textColor()))
      ..addText(_text());
    <span style="color:#66d9ef">final</span> ui.ParagraphConstraints constraints <span style="color:#f92672">=</span> ui.ParagraphConstraints(width: width);
    <span style="color:#66d9ef">final</span> ui.Paragraph paragraph <span style="color:#f92672">=</span> builder.build()..layout(constraints);
    <span style="color:#66d9ef">final</span> <span style="color:#66d9ef">double</span> x <span style="color:#f92672">=</span> (width <span style="color:#f92672">-</span> paragraph.width) <span style="color:#f92672">/</span> <span style="color:#ae81ff">2</span>;
    <span style="color:#66d9ef">final</span> <span style="color:#66d9ef">double</span> y <span style="color:#f92672">=</span> (height <span style="color:#f92672">-</span> paragraph.height) <span style="color:#f92672">/</span> <span style="color:#ae81ff">2</span>;
    canvas.drawParagraph(paragraph, Offset(x, y));
  }

  <span style="color:#75715e">/// 绘制圆
</span><span style="color:#75715e"></span>  <span style="color:#66d9ef">void</span> _drawCircle(Canvas canvas, Size size) {
    canvas.drawArc(Rect.fromCircle(center: Offset(radius, radius), radius: radius), <span style="color:#ae81ff">2</span> <span style="color:#f92672">*</span> pi <span style="color:#f92672">/</span> <span style="color:#ae81ff">4</span> <span style="color:#f92672">*</span> <span style="color:#ae81ff">3</span>, <span style="color:#ae81ff">2</span> <span style="color:#f92672">*</span> pi <span style="color:#f92672">*</span> circle,
        <span style="color:#66d9ef">false</span>, paintArc);
  }

  <span style="color:#75715e">/// 绘制矩形
</span><span style="color:#75715e"></span>  <span style="color:#66d9ef">void</span> _drawRectangle(Canvas canvas, Size size) {
    <span style="color:#66d9ef">final</span> <span style="color:#66d9ef">double</span> width <span style="color:#f92672">=</span> size.width;
    <span style="color:#66d9ef">final</span> <span style="color:#66d9ef">double</span> height <span style="color:#f92672">=</span> size.height;
    <span style="color:#66d9ef">final</span> <span style="color:#66d9ef">double</span> halfWidth <span style="color:#f92672">=</span> width <span style="color:#f92672">/</span> <span style="color:#ae81ff">2</span>;
    <span style="color:#66d9ef">if</span> (endTopLine <span style="color:#f92672">&gt;</span> <span style="color:#ae81ff">0</span>) {
      canvas.drawLine(Offset(halfWidth, <span style="color:#ae81ff">0</span>), Offset(halfWidth <span style="color:#f92672">+</span> halfWidth <span style="color:#f92672">*</span> endTopLine, <span style="color:#ae81ff">0</span>), paintArc);
    }
    <span style="color:#66d9ef">if</span> (rightLine <span style="color:#f92672">&gt;</span> <span style="color:#ae81ff">0</span>) {
      canvas.drawLine(Offset(width, <span style="color:#ae81ff">0</span>), Offset(width, height <span style="color:#f92672">*</span> rightLine), paintArc);
    }
    <span style="color:#66d9ef">if</span> (bottomLine <span style="color:#f92672">&gt;</span> <span style="color:#ae81ff">0</span>) {
      canvas.drawLine(Offset(width, height), Offset(width <span style="color:#f92672">-</span> width <span style="color:#f92672">*</span> bottomLine, height), paintArc);
    }
    <span style="color:#66d9ef">if</span> (leftLine <span style="color:#f92672">&gt;</span> <span style="color:#ae81ff">0</span>) {
      canvas.drawLine(Offset(<span style="color:#ae81ff">0</span>, height), Offset(<span style="color:#ae81ff">0</span>, height <span style="color:#f92672">-</span> height <span style="color:#f92672">*</span> leftLine), paintArc);
    }
    <span style="color:#66d9ef">if</span> (startTopLine <span style="color:#f92672">&gt;</span> <span style="color:#ae81ff">0</span>) {
      canvas.drawLine(Offset.zero, Offset(halfWidth <span style="color:#f92672">*</span> startTopLine, <span style="color:#ae81ff">0</span>), paintArc);
    }
  }

  <span style="color:#75715e">/// 绘制圆角矩形
</span><span style="color:#75715e"></span>  <span style="color:#66d9ef">void</span> _drawArcRectangle(Canvas canvas, Size size) {
    <span style="color:#66d9ef">final</span> <span style="color:#66d9ef">double</span> width <span style="color:#f92672">=</span> size.width;
    <span style="color:#66d9ef">final</span> <span style="color:#66d9ef">double</span> height <span style="color:#f92672">=</span> size.height;
    <span style="color:#66d9ef">final</span> <span style="color:#66d9ef">double</span> halfWidth <span style="color:#f92672">=</span> width <span style="color:#f92672">/</span> <span style="color:#ae81ff">2</span>;
    <span style="color:#66d9ef">final</span> <span style="color:#66d9ef">double</span> internalWidth <span style="color:#f92672">=</span> width <span style="color:#f92672">-</span> radius;
    <span style="color:#66d9ef">final</span> <span style="color:#66d9ef">double</span> internalHeight <span style="color:#f92672">=</span> height <span style="color:#f92672">-</span> radius;
    <span style="color:#66d9ef">final</span> <span style="color:#66d9ef">double</span> sweepAngle <span style="color:#f92672">=</span> pi <span style="color:#f92672">/</span> <span style="color:#ae81ff">2</span>;

    <span style="color:#75715e">// 矩形顶部横线，从中间开始
</span><span style="color:#75715e"></span>    <span style="color:#66d9ef">if</span> (endTopLine <span style="color:#f92672">&gt;</span> <span style="color:#ae81ff">0</span>) {
      canvas.drawLine(Offset(halfWidth, <span style="color:#ae81ff">0</span>), Offset(halfWidth <span style="color:#f92672">+</span> (halfWidth <span style="color:#f92672">-</span> radius) <span style="color:#f92672">*</span> endTopLine, <span style="color:#ae81ff">0</span>), paintArc);
    }

    <span style="color:#75715e">// 右上角圆角
</span><span style="color:#75715e"></span>    <span style="color:#66d9ef">if</span> (topRightArc <span style="color:#f92672">&gt;</span> <span style="color:#ae81ff">0</span>) {
      canvas.drawArc(Rect.fromCircle(center: Offset(internalWidth, radius), radius: radius), <span style="color:#ae81ff">2</span> <span style="color:#f92672">*</span> pi <span style="color:#f92672">/</span> <span style="color:#ae81ff">4</span> <span style="color:#f92672">*</span> <span style="color:#ae81ff">3</span>,
          sweepAngle <span style="color:#f92672">*</span> topRightArc, <span style="color:#66d9ef">false</span>, paintArc);
    }

    <span style="color:#75715e">// 矩形右边竖线
</span><span style="color:#75715e"></span>    <span style="color:#66d9ef">if</span> (rightLine <span style="color:#f92672">&gt;</span> <span style="color:#ae81ff">0</span>) {
      canvas.drawLine(Offset(width, radius), Offset(width, radius <span style="color:#f92672">+</span> (height <span style="color:#f92672">-</span> <span style="color:#ae81ff">2</span> <span style="color:#f92672">*</span> radius) <span style="color:#f92672">*</span> rightLine), paintArc);
    }

    <span style="color:#75715e">// 右下角圆角
</span><span style="color:#75715e"></span>    <span style="color:#66d9ef">if</span> (bottomRightArc <span style="color:#f92672">&gt;</span> <span style="color:#ae81ff">0</span>) {
      canvas.drawArc(Rect.fromCircle(center: Offset(internalWidth, internalHeight), radius: radius), <span style="color:#ae81ff">0</span>,
          sweepAngle <span style="color:#f92672">*</span> bottomRightArc, <span style="color:#66d9ef">false</span>, paintArc);
    }

    <span style="color:#75715e">// 矩形底部横线
</span><span style="color:#75715e"></span>    <span style="color:#66d9ef">if</span> (bottomLine <span style="color:#f92672">&gt;</span> <span style="color:#ae81ff">0</span>) {
      canvas.drawLine(
          Offset(internalWidth, height), Offset(internalWidth <span style="color:#f92672">-</span> ((width <span style="color:#f92672">-</span> <span style="color:#ae81ff">2</span> <span style="color:#f92672">*</span> radius) <span style="color:#f92672">*</span> bottomLine), height), paintArc);
    }

    <span style="color:#75715e">// 左下角圆角
</span><span style="color:#75715e"></span>    <span style="color:#66d9ef">if</span> (bottomLeftArc <span style="color:#f92672">&gt;</span> <span style="color:#ae81ff">0</span>) {
      canvas.drawArc(Rect.fromCircle(center: Offset(radius, internalHeight), radius: radius), pi <span style="color:#f92672">/</span> <span style="color:#ae81ff">2</span>,
          sweepAngle <span style="color:#f92672">*</span> bottomLeftArc, <span style="color:#66d9ef">false</span>, paintArc);
    }

    <span style="color:#75715e">// 矩形左边竖线
</span><span style="color:#75715e"></span>    <span style="color:#66d9ef">if</span> (leftLine <span style="color:#f92672">&gt;</span> <span style="color:#ae81ff">0</span>) {
      canvas.drawLine(
          Offset(<span style="color:#ae81ff">0</span>, internalHeight), Offset(<span style="color:#ae81ff">0</span>, internalHeight <span style="color:#f92672">-</span> ((height <span style="color:#f92672">-</span> <span style="color:#ae81ff">2</span> <span style="color:#f92672">*</span> radius) <span style="color:#f92672">*</span> leftLine)), paintArc);
    }

    <span style="color:#75715e">// 左上角圆角
</span><span style="color:#75715e"></span>    <span style="color:#66d9ef">if</span> (topLeftArc <span style="color:#f92672">&gt;</span> <span style="color:#ae81ff">0</span>) {
      canvas.drawArc(Rect.fromCircle(center: Offset(radius, radius), radius: radius), pi, sweepAngle <span style="color:#f92672">*</span> topLeftArc,
          <span style="color:#66d9ef">false</span>, paintArc);
    }

    <span style="color:#75715e">// 矩形顶部横线，从0开始到中间
</span><span style="color:#75715e"></span>    <span style="color:#66d9ef">if</span> (startTopLine <span style="color:#f92672">&gt;</span> <span style="color:#ae81ff">0</span>) {
      canvas.drawLine(Offset(radius, <span style="color:#ae81ff">0</span>), Offset(radius <span style="color:#f92672">+</span> (width <span style="color:#f92672">-</span> <span style="color:#ae81ff">2</span> <span style="color:#f92672">*</span> radius) <span style="color:#f92672">/</span> <span style="color:#ae81ff">2</span> <span style="color:#f92672">*</span> startTopLine, <span style="color:#ae81ff">0</span>), paintArc);
    }
  }

  <span style="color:#75715e">/// 绘制左右整个圆角矩形
</span><span style="color:#75715e"></span>  <span style="color:#66d9ef">void</span> _drawWidthArcRectangle(Canvas canvas, Size size) {
    <span style="color:#66d9ef">final</span> <span style="color:#66d9ef">double</span> width <span style="color:#f92672">=</span> size.width;
    <span style="color:#66d9ef">final</span> <span style="color:#66d9ef">double</span> height <span style="color:#f92672">=</span> size.height;
    <span style="color:#66d9ef">final</span> <span style="color:#66d9ef">double</span> halfWidth <span style="color:#f92672">=</span> width <span style="color:#f92672">/</span> <span style="color:#ae81ff">2</span>;
    <span style="color:#66d9ef">final</span> <span style="color:#66d9ef">double</span> halfHeight <span style="color:#f92672">=</span> height <span style="color:#f92672">/</span> <span style="color:#ae81ff">2</span>;
    <span style="color:#66d9ef">final</span> <span style="color:#66d9ef">double</span> internalWidth <span style="color:#f92672">=</span> width <span style="color:#f92672">-</span> radius;
    <span style="color:#66d9ef">final</span> <span style="color:#66d9ef">double</span> sweepAngle <span style="color:#f92672">=</span> pi;

    <span style="color:#75715e">// 矩形顶部横线，从中间开始
</span><span style="color:#75715e"></span>    <span style="color:#66d9ef">if</span> (endTopLine <span style="color:#f92672">&gt;</span> <span style="color:#ae81ff">0</span>) {
      canvas.drawLine(Offset(halfWidth, <span style="color:#ae81ff">0</span>), Offset(halfWidth <span style="color:#f92672">+</span> (halfWidth <span style="color:#f92672">-</span> radius) <span style="color:#f92672">*</span> endTopLine, <span style="color:#ae81ff">0</span>), paintArc);
    }

    <span style="color:#75715e">// 右上角圆角
</span><span style="color:#75715e"></span>    <span style="color:#66d9ef">if</span> (topRightArc <span style="color:#f92672">&gt;</span> <span style="color:#ae81ff">0</span>) {
      canvas.drawArc(Rect.fromCircle(center: Offset(internalWidth, halfHeight), radius: radius), <span style="color:#ae81ff">2</span> <span style="color:#f92672">*</span> pi <span style="color:#f92672">/</span> <span style="color:#ae81ff">4</span> <span style="color:#f92672">*</span> <span style="color:#ae81ff">3</span>,
          sweepAngle <span style="color:#f92672">*</span> topRightArc, <span style="color:#66d9ef">false</span>, paintArc);
    }
    <span style="color:#75715e">// 矩形底部横线
</span><span style="color:#75715e"></span>    <span style="color:#66d9ef">if</span> (bottomLine <span style="color:#f92672">&gt;</span> <span style="color:#ae81ff">0</span>) {
      canvas.drawLine(
          Offset(internalWidth, height), Offset(internalWidth <span style="color:#f92672">-</span> ((width <span style="color:#f92672">-</span> <span style="color:#ae81ff">2</span> <span style="color:#f92672">*</span> radius) <span style="color:#f92672">*</span> bottomLine), height), paintArc);
    }

    <span style="color:#75715e">// 左上角圆角
</span><span style="color:#75715e"></span>    <span style="color:#66d9ef">if</span> (topLeftArc <span style="color:#f92672">&gt;</span> <span style="color:#ae81ff">0</span>) {
      canvas.drawArc(Rect.fromCircle(center: Offset(radius, halfHeight), radius: radius), pi <span style="color:#f92672">/</span> <span style="color:#ae81ff">2</span>,
          sweepAngle <span style="color:#f92672">*</span> topLeftArc, <span style="color:#66d9ef">false</span>, paintArc);
    }

    <span style="color:#75715e">// 矩形顶部横线，从0开始到中间
</span><span style="color:#75715e"></span>    <span style="color:#66d9ef">if</span> (startTopLine <span style="color:#f92672">&gt;</span> <span style="color:#ae81ff">0</span>) {
      canvas.drawLine(Offset(radius, <span style="color:#ae81ff">0</span>), Offset(radius <span style="color:#f92672">+</span> (width <span style="color:#f92672">-</span> <span style="color:#ae81ff">2</span> <span style="color:#f92672">*</span> radius) <span style="color:#f92672">/</span> <span style="color:#ae81ff">2</span> <span style="color:#f92672">*</span> startTopLine, <span style="color:#ae81ff">0</span>), paintArc);
    }
  }

  <span style="color:#960050;background-color:#1e0010">@</span>override
  <span style="color:#66d9ef">void</span> paint(Canvas canvas, Size size) {
    <span style="color:#75715e">// 绘制圆角矩形
</span><span style="color:#75715e"></span>    _drawRect(canvas, size);

    <span style="color:#75715e">// 绘制文字文字
</span><span style="color:#75715e"></span>    _drawText(canvas, size);

    <span style="color:#66d9ef">if</span> (status <span style="color:#f92672">==</span> Status.animating) {
      <span style="color:#75715e">// 绘制圆
</span><span style="color:#75715e"></span>      <span style="color:#66d9ef">if</span> (isCircle) {
        _drawCircle(canvas, size);
        <span style="color:#66d9ef">return</span>;
      }
      <span style="color:#75715e">// 绘制矩形
</span><span style="color:#75715e"></span>      <span style="color:#66d9ef">if</span> (isRectangle) {
        _drawRectangle(canvas, size);
        <span style="color:#66d9ef">return</span>;
      }

      <span style="color:#75715e">// 绘制圆角矩形
</span><span style="color:#75715e"></span>      <span style="color:#66d9ef">if</span> (isArcRectangle) {
        _drawArcRectangle(canvas, size);
        <span style="color:#66d9ef">return</span>;
      }

      <span style="color:#75715e">// 绘制左右整个圆角矩形
</span><span style="color:#75715e"></span>      <span style="color:#66d9ef">if</span> (isWidthArc) {
        _drawWidthArcRectangle(canvas, size);
        <span style="color:#66d9ef">return</span>;
      }

      <span style="color:#75715e">// 绘制上下整个圆角矩形
</span><span style="color:#75715e"></span>
      <span style="color:#75715e">// 绘制上下左右圆角矩形
</span><span style="color:#75715e"></span>
    }
  }

  <span style="color:#960050;background-color:#1e0010">@</span>override
  <span style="color:#66d9ef">bool</span> shouldRepaint(covariant CustomPainter oldDelegate) {
    <span style="color:#66d9ef">return</span> <span style="color:#66d9ef">true</span>;
  }
}

</code></pre></div><p>法尔</p>
<pre><code>import 'dart:math';
import 'dart:ui';

import 'package:flutter/material.dart';
import 'package:flutter/rendering.dart';
import 'package:http/http.dart' as http;
import 'dart:convert' as convert;

void main() {
  runApp(MyApp());
}

class MyApp extends StatelessWidget {
  // This widget is the root of your application.
  @override
  Widget build(BuildContext context) {
    return MaterialApp(
      title: 'Flutter Demo',
      theme: ThemeData(
        primarySwatch: Colors.blue,
        visualDensity: VisualDensity.adaptivePlatformDensity,
      ),
      home: MyHomePage(title: 'Flutter Demo Home Page'),
    );
  }
}

class MyHomePage extends StatefulWidget {
  MyHomePage({Key key, this.title}) : super(key: key);

  final String title;

  @override
  _MyHomePageState createState() =&gt; _MyHomePageState();
}

class _MyHomePageState extends State&lt;MyHomePage&gt; {
  bool _zoomed = false; //缩放
  @override
  Widget build(BuildContext context) {
    return Scaffold(
        appBar: AppBar(
          title: Text(&quot;计时器&quot;),
        ),
        body: Center(
          child: Transform.scale(
            scale: _zoomed ? 2.8 : 1.0,
            child: Column(
              mainAxisAlignment: MainAxisAlignment.center,
              children: [
                CountdownButton(
                  duration: Duration(
                    seconds: 5,
                  ),
                  width: 150,
                  height: 40,
                  radius: 20,
                ),
                const SizedBox(
                  height: 24,
                ),
                CountdownButton(
                  duration: Duration(
                    seconds: 60,
                  ),
                  width: 80,
                  height: 80,
                  radius: 40,
                ),
                const SizedBox(
                  height: 24,
                ),
                CountdownButton(
                  duration: Duration(
                    seconds: 5,
                  ),
                  width: 80,
                  height: 40,
                  radius: 0,
                ),
              ],
            ),
          ),
        ));
  }
}

class CountdownButton extends StatefulWidget {
  final Duration duration;
  final double width, height, radius;
  CountdownButton(
      {Key key, this.duration, this.height, this.radius, this.width})
      : super(key: key);

  @override
  _CountdownButtonState createState() =&gt; _CountdownButtonState();
}

class _CountdownButtonState extends State&lt;CountdownButton&gt;
    with SingleTickerProviderStateMixin {
  AnimationController _controller; // late AnimationController _controller;
  int _stage = 0;

  @override
  void initState() {
    // TODO: implement initState
    super.initState();
    _controller = AnimationController(vsync: this, duration: widget.duration)
      ..addStatusListener((status) {
        if (status == AnimationStatus.completed) {}

        setState(() {
          _stage = 2;
        });
      });
  }

  @override
  void dispose() {
    // TODO: implement dispose
    _controller.dispose();
    super.dispose();
  }

  @override
  Widget build(BuildContext context) {
    String label;
    Color textColor;
    Color bgColor;

    switch (_stage) {
      case 0:
        label = &quot;send&quot;;
        textColor = Colors.white;
        bgColor = Colors.blue;

        break;
      case 1:
        label = &quot;canel&quot;;
        // textColor = Colors.white;
        // bgColor = Colors.blue;

        break;
      case 2:
        label = &quot;done&quot;;
        textColor = Colors.grey;
        // bgColor = Colors.blue;

        break;
      default:
    }
    return Stack(
      children: [
        CustomPaint(
          painter: BorderPainer(
            buttonWidth: widget.width,
            buttonHeight: widget.height,
            buttonRadius: widget.radius,
            animation: _controller,
          ),
        ),
        SizedBox(
          width: widget.width,
          height: widget.height,
          child: Container(
            decoration: BoxDecoration(
              borderRadius: BorderRadius.circular(widget.radius),
            ),
            child: FlatButton(
              textColor: textColor,
              focusColor: bgColor,
              onPressed: () {
                if (_stage == 0) {
                  _controller.forward(from: 0.0);

                  setState(() {
                    _stage = 1;
                  });
                } else {
                  _controller.reset();
                  setState(() {
                    _stage = 0;
                  });
                }
              },
              child: Text(label),
            ),
          ),
        )
      ],
    );
  }
}

class BorderPainer extends CustomPainter {
  final double buttonWidth;
  final double buttonHeight;
  final double buttonRadius;
  final Animation&lt;double&gt; animation;

  final Paint bluePaint = Paint()
    ..style = PaintingStyle.stroke
    ..strokeWidth = 2.0
    ..color = Colors.blue;
  final Paint greyaint = Paint()
    ..style = PaintingStyle.stroke
    ..strokeWidth = 2.0
    ..color = Colors.red;
  RRect shape; //late

  PathMetric pathMetric; //late

  BorderPainer(
      {this.buttonWidth, this.buttonHeight, this.buttonRadius, this.animation})
      : super(repaint: animation) {
    shape = RRect.fromRectAndRadius(
        Rect.fromCenter(
            center: Offset.zero, width: buttonWidth, height: buttonHeight),
        Radius.circular(buttonRadius));

    final path = Path()..addRRect(shape);
    pathMetric = path.computeMetrics().single; //只有1行
  }

  @override
  void paint(Canvas canvas, Size size) {
    final path = Path();
    final totalLength = pathMetric.length - 100; //得到长度

    final currentLength = totalLength * animation.value;
    // path.addPath(pathMetric.extractPath(0, currentLength), Offset.zero); //简单

    final startingPoint =
        totalLength / 4 + max(buttonHeight / 2 - buttonRadius, 0);
    path.addPath(
        pathMetric.extractPath(startingPoint, currentLength + startingPoint),
        Offset.zero);

    canvas.translate(
      buttonWidth / 2,
      buttonHeight / 2,
    );
    canvas.drawRRect(
      shape,
      bluePaint,
    );
    canvas.drawPath(path, greyaint);
  }

  @override
  bool shouldRepaint(BorderPainer oldDelegate) =&gt; false;

  // @override
  // bool shouldRebuildSemantics(BorderPainer oldDelegate) =&gt; false;
}

</code></pre>
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